AN4650 datasheet(43/102 Pages) STMICROELECTRONICS

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AN4650

Interrupt generation

102

Hereafter an example which implements the SW routine for 6D orientation detection.

4.4.2

4D orientation detection

The 4D direction function is a subset of the 6D function especially defined to be

implemented in mobile devices for portrait and landscape computation. It can be enabled by

setting the D4D_EN bit of the TAP_THS_6D register to 1. In this configuration, the Z-axis

position detection is disabled, therefore reducing position recognition to cases (a), (b), (c),

and (d) of Table 31.

4.5

Single-tap and double-tap recognition

The single-tap and double-tap recognition functions featured in the LSM6DS3 help to create

a man-machine interface with little software loading. The device can be configured to output

an interrupt signal on a dedicated pin when tapped in any direction.

If the sensor is exposed to a single input stimulus, it generates an interrupt request on the

inertial interrupt pin INT1 and/or INT2. A more advanced feature allows the generation of an

interrupt request when a double input stimulus with programmable time between the two

events is recognized, enabling a mouse button-like function.

In the LSM6DS3 device the single-tap and double-tap recognition functions use the slope

between two consecutive acceleration samples to detect the tap events; the slope data is

computed using the following formula:

slope(tn) = [ acc(tn) - acc(tn-1) ] / 2

This function can be fully programmed by the user in terms of expected amplitude and

timing of the slope data by means of a dedicated set of registers.

Single and double-tap recognition work independently of the selected output data rate.

Recommended accelerometer ODRs for these functions are 416 Hz and 833 Hz.

Table 31. D6D_SRC register in 6D positions

Case

D6D_IA

(a)

1001000

(b)

1000001

(c)

1000010

(d)

1000100

(e)

1100000

(f)

1010000

Write 60h into CTRL1_XL

// Turn on the accelerometer

// ODR_XL = 416 Hz, FS_XL = 2g

Write 40h into TAP_THS_6D

// Set 6D threshold (SIXD_THS[1:0] = 10b = 60 degrees)

Write 10h into TAP_CFG

// Enable LPF2 filter

Write 01h into CTRL8_XL

// Apply LPF2 filter to 6D functionality

Write 04h into MD1_CFG

// 6D interrupt driven to INT1 pin

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